Add procmem slicing and refactor to make proper MemoryBuffer interface

[psrok1]

After looking at #119 I found that bb4c7d48773b21c62885d0206c9414176c254e6104b4a0ffe730aa570b424948 is not actually b = open("x.exe").read(); b = b * 100, but set of different binaries/

The main problem was that procmempe.from_memory(p, base=0x100) doesn't make m that starts from 0x100. It just makes reference to the same memory and sets imgbase to 0x100. It means that first binary bb4c7d48773b21c62885d0206c9414176c254e6104b4a0ffe730aa570b424948 was ripped n times, so carving was not really working as intended 😅

In this PR I moved the "memory management" part to the separate set of classes MemoryBuffer and implemented proper slicing.

ProcessMemory has implemented one extra method slicev that allows to get a slice of memory view over MemoryBuffer. The only limitation is that slice must be within single region.

Along with #121 reducing memory footprint, it should work a bit more correctly.

[psrok1]

This requires a bit different approach.

Main issue is that memoryview holds a pointer to the underlying buffer and need to be explicitly released before releasing the main buffer

  File "/usr/local/lib/python3.10/site-packages/malduck/extractor/extract_manager.py", line 105, in push_file
    with ProcessMemory.from_file(filepath, base=base) as p:
  File "/usr/local/lib/python3.10/site-packages/malduck/procmem/procmem.py", line 106, in __exit__
    self.close()
  File "/usr/local/lib/python3.10/site-packages/malduck/procmem/procmem.py", line 121, in close
    self.memory.release()
  File "/usr/local/lib/python3.10/site-packages/malduck/procmem/membuf.py", line 100, in release
    self.mapped_buf.close()
BufferError: cannot close exported pointers exist

In many modules and components we don't keep track on all derived procmems and we rely on GC there. When we release memory allocated by procmem.from_file, we just assume that there are no active references to procmems produced by procmem.from_memory that are referencing the same memory.

[psrok1]

Added reference tracking of mmap slices in ab61f36 and c684022

When MmapMemoryBuffer is going to be closed and underlying mmap is going to be released, MMapMemoryBuffer has weakrefset to all slice objects (MmapSliceMemoryBuffer) that keep reference to that mmap and are not already GC'd/explicitly released. This weakrefset is used to call release() on all these slices, so we can safely release the main mmap allocation.